Rotary cam actuated linear peristaltic pump

ABSTRACT

A rotary cam actuated linear peristaltic pump includes a plurality of cams which actuate a plurality of pistons. The cams apply a force to the piston by way of a lifter for providing mechanical advantage so that a smaller motor may be used to rotate the cam. Each piston of a plurality of pistons is sequentially raised to the extended position to squeeze a tube so as to flow fluid through the tube.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND

The embodiments discussed herein relate to a peristaltic pump.

Peristaltic pumps are typically used in medical applications formetering intravenous infusion of a medication into a patient.Peristaltic pumps may also be used for withdrawing fluid such as inwound drainage procedures. To this end, various linear and curvilinearperistaltic pumps have been introduced into the market place.

For example, the curvilinear peristaltic pump described in U.S. Pat. No.6,164,921 (hereinafter '921 patent) was introduced into the marketplace.The entire contents of the '921 patent is expressly incorporated hereinby reference. The first named inventor of the '921 patent is theinventor of the device described below in the detailed descriptionsection. As shown in FIG. 7 of the '921 patent, a flexible tubing isinserted between a plurality of fingers and a platen. The fingers arearranged in a curved pattern. Also, the bottom surface of the platenwhich work in conjunction with the fingers is also curved and matched tothe curvature of the plurality of fingers. As the cam rotates, the lobesof the cam push the fingers into the tube disposed between the fingersand the bottom surface of the platen in a rolling manner to urge fluidthrough the tube.

Unfortunately, the peristaltic pump disclosed in the '921 patent hascertain limitations. To operate the pump, the tube is installed betweenthe platen and the fingers of the pump by opening the platen, fitting alocator pin and a shut off valve into recesses formed in a body of thepump and closing the platen. In doing so, it is difficult to fit thelocator pin and the shut off valve into the recesses due to the curvedconfiguration of the fingers and the curved bottom surface of theplaten. Moreover, the tube is typically installed on the pump when thepump is hung on a stand next to a patient. However, the pump is topheavy causing the pump to be unstable and shift during installation ofthe tube.

Another limitation of the device disclosed in the '921 patent is thatthe flow rate through the pump is low fluid in the range of 600 mL. Theflow rate of the pump is dependent on a variety of factors such as cyclespeed of the fingers, the size of the tube, etc. To increase the fluidflow rate through the pump, these factors must be improved by increasingthe cyclical speed of the fingers, increasing the size of the tube, etc.Unfortunately, to do so, the size of the motor must be enlarged tohandle the increased load. The pump disclosed in the '921 patent isrelatively heavy. Enlarging the motor would undesirably increase theweight of the pump and may cause further instability.

Accordingly, there is a need in the art for an improved peristalticpump.

BRIEF SUMMARY

The embodiments disclosed herein address the needs discussed above,discussed below and those that are known in the art.

A rotary cam actuated linear peristaltic pump is disclosed. The pump mayhave a plurality of pistons that are traversable between extended andretracted positions. The pistons are traversed toward the extendedposition in a sequential manner through a plurality of cams. Cam lobesof each of the cams are angularly offset with respect to the prior andsubsequent cams. The cam lobes are operative to traverse the pistonstoward the extended position. Since the cam lobes are offset, thepistons are traversed to the extended position in a wave format duringrotation of the cams. A tube is disposed between the piston and aplaten. As the pistons move to the extended position, the piston and theplaten squeeze the tube so as to occlude the tube and prevent the flowof fluid through the occluded portion thereof. Initially, a first camtraverses a first piston to occlude the tube. The next cam traverses thenext piston towards the extended position to also occlude the tube.However, during this period of time, the first piston prevents fluidflow through the tube. Since the second piston is applying pressure tothe tube, the fluid flows to the path of least resistance, specifically,to the opposite side of the first piston. The third and subsequentpistons continue this movement until the fluid is pushed out of thepump.

The cams are mounted to a rotating cam shaft. The cam shaft is rotatedwith a motor. A motor and the cam shaft are in mechanical communicationwith each other by way of a worm drive and a worm gear. The worm driveand worm gear provide a gear reduction (i.e., mechanical advantage) sothat a smaller motor is capable of running the pump. Moreover, the wormdrive and worm gear prevent reverse rotation of the cam shaft duringoperation. This prevents fluid from back flowing through the tube. Thecams also raise lifters which provide a mechanical advantage to reducethe load required to lift or traverse the pistons to the extendedposition. In particular, the pistons are preferably disposed about halfway between a pivot point of the lifter and the cam. As such, the camneed only generate about one half the force to lift the piston to raisethe piston since the lifter functions as a lever. Accordingly, a smallermotor can flow fluid through the tube at a greater rate (e.g., 1500 mL),as discussed below.

A plurality of cams are stacked upon a common rotating shaft driven bythe motor. Each of the cams may have a plurality of lobes which raisethe lifters and traverse the pistons to the extended position. Thecorresponding lobes of adjacent cams are angularly displaced so that oneset of corresponding lobes of the plurality of cams provide one pumpcycle. If there are four lobes on each of the cams then there are fourpump cycles.

More particularly, a peristaltic pump for flowing fluid through a lumenof a tube wherein the tube may define a diameter is disclosed. The pumpmay comprise a plurality of pistons, a plurality of lifters, a platen, arotateable cam shaft, and a plurality of cams. The plurality of pistonsmay be linearly arranged adjacent to each other in a straightconfiguration. Each of the plurality of pistons may define opposed firstand second ends. Each of the plurality of pistons may be traversedbetween extended and retracted positions.

Each of the lifters is pivotable about a pivot axis.

The platen may be disposed adjacent to the first ends of the pluralityof pistons. The platen may be generally parallel to the plurality ofpistons. A gap between a first end of a piston and the platen may beabout equal to or more than a diameter of the tube when the piston istraversed to the retracted position. The gap may be smaller than thediameter of the tube when the piston is traversed to the extendedposition.

The rotatable cam shaft may be generally parallel to the plurality ofpistons.

The plurality of cams may be mounted to the rotatable cam shaft. Each ofthe cams may have a cam lobe. The cam lobes of the plurality of cams maybe disposed adjacent to the second end portions of the lifters with thesecond ends of the pistons positioned in between the second end portionsof the lifters and the pivot axis of the lifters. As the cam shaftrotates, the lobes raise the lifters which provide a mechanicaladvantage to traverse the pistons to the extended position. The cams areangularly displaced with respect to the adjacent cam. The pistons aresequentially traversed to the extended position to flow fluid throughthe tube.

The platen may be traversed between an open position for inserting orremoving the tube between the plurality of pistons and the platen and aclosed position for flowing fluid through the lumen of the tube when thetube is disposed between the platen and the plurality of pistons.

The pump may further comprise a worm gear attached to the cam shaft; aworm drive engaged to the worm gear; and a motor attached to the wormdrive for rotating the worm drive.

The plurality of pistons may linearly occlude the tube as each one ofthe plurality of pistons is sequentially traversed to the extendedposition due to the progressive angular displacement of the cams.

Each of the cams may have four lobes spaced 90 degrees apart from eachother. The total angular displacement of the plurality of cams may beabout 90 degrees.

The cam lobes of the cams may have a curved peak surface defined by anarc having a center about a rotating axis of the cam shaft and the cams.The curved peak surfaces of cam lobes of adjacent cams may be offset andoverlap one another to urge fluid through the tube in one direction.

The pistons may reciprocate between extended and retracted positionsabout a common axis. The common axis of the reciprocating pistons, aflat surface of the platen and a rotating axis of the cam shaft may beparallel with each other.

Moreover, a method of operating a peristaltic pump for flowing fluidthrough a lumen of a tube is disclosed. The method may comprise thesteps of disposing the tube between a platen and a plurality of pistonswherein the tube is straight and parallel to the platen and theplurality of pistons; sequentially traversing the plurality of pistonsto an extended position; occluding the tube linearly down the tube whenthe pistons are sequentially traversed to the extended position; andpushing the piston back to a retracted position due to resiliency of thetube.

The disposing step may further include the step of traversing the platenfrom an open position to a closed position.

The method may further comprise the step of aligning the tube to beparallel to the platen and a cam shaft. The method may also furthercomprise the step of rotating a cam shaft on which a plurality of camare mounted. Each of the cams may have a cam lobe angularly offset fromcam lobes of adjacent cams. The method may further comprise the step ofactuating a plurality of lifters to sequentially traverse the pluralityof pistons to the extended position.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodimentsdisclosed herein will be better understood with respect to the followingdescription and drawings, in which like numbers refer to like partsthroughout, and in which:

FIG. 1 is a perspective view of a rotary cam actuated linear peristalticpump;

FIG. 2 is an exploded perspective view of the pump shown in FIG. 1before a tube is installed into the pump;

FIG. 3 is a perspective view of the pump shown in FIG. 2 with a handleof a latch being opened;

FIG. 4 is a perspective view of the pump shown in FIG. 3 with a platendisposed in an open position;

FIG. 5 is a perspective view of the pump shown in FIG. 4 alongside thetube to be inserted into the pump;

FIG. 6 is a perspective view of the pump with the tube mounted to thepump;

FIG. 7 is a perspective view of the pump with the platen disposed in aclosed position over the tube;

FIG. 7A is a cross sectional view of the pump shown in FIG. 7 with thehandle of the latch disposed in an open position;

FIG. 7B is a cross sectional view of the pump shown in FIG. 7 with thehandle of the latch disposed in a closed position;

FIG. 8 is a perspective view of the pump shown in FIG. 7 with the handlein the closed position;

FIG. 9 is a cross sectional perspective view of the pump shown in FIG.8;

FIG. 9A is a side view of cam lobes of adjacent cams shown in FIG. 9;

FIG. 10 is a longitudinal cross sectional view of the pump shown in FIG.8;

FIG. 11 is a lateral cross sectional view of the pump shown in FIG. 8;

FIG. 12 is an exploded perspective view of the pump shown in FIG. 1;

FIG. 13 is a perspective view of a piston;

FIG. 13A is a front view of the piston shown in FIG. 13;

FIG. 14 is a perspective view of one cam of a stack of cams; and

FIG. 14A is a side view of the cam shown in FIG. 14.

DETAILED DESCRIPTION

Referring now to the drawings, a peristaltic pump 10 is shown. Theperistaltic pump 10 is operative to receive a tube 12 that can flowfluid therethrough. As shown in FIG. 10, a plurality of pistons 14 a-hare traversable between an extended position (see piston 14 a) and aretracted position (see piston 14 d). The pistons 14 a-h aresequentially traversed to the extended position from the retractedposition from the right to the left to flow fluid through the tube 12 inthe direction of arrow 16. The pistons 14 a-h sequentially squeeze thetube 12 to urge the fluid through the tube 12. The pistons 14 a-h movein a wave format as cams 18 a-h are rotated in the direction of arrow 22to continuously urge the fluid through the tube 12. The plurality ofcams 18 a-h, n are mounted to a cam shaft 20 that rotates in thedirection of arrow 22 shown in FIG. 10. Each of the cams 18 a-h havemultiple lobes 24 a-d (see FIG. 11). The lobes 24 a-d of the cams 18 a-hlift lifters 26 a-h which act as a lever to push the piston 14 towardthe tube 12. The piston 12 and a platen 28 squeeze (see FIG. 11) thetube 12 to occlude the tube 12 in the direction of arrow 16 to push thefluid in the direction 16 through the tube 12. When the peaks of the camlobes 24 a-d have passed the lifter 26, the resiliency of the tube 12pushes the piston 14 back to the retracted position and allows fluid toflow through the tube 12 behind occluded section of the tube 12.Accordingly, as the pistons 14 a-h sequentially occlude the tube 12,fluid is urged through the tube 12 in the direction of arrow 16 andadditional fluid is primed into the system to flow more fluid out of thepump 10 through the tube 12.

More particularly, the pump 10 may be hung vertically during use asshown in FIG. 1. In the vertical position, the tube 12 is easilyinstalled into the peristaltic pump 10 and removed therefrom since thetube 12 has a straight configuration in the pump 10, as shown anddiscussed further below. The pump 10 may have a hook or other hangingdevice that allows the peristaltic pump 10 to be hung on a stand orother mechanism. The fluid flows through the tube 12 in the direction ofarrow 16. However, it is also contemplated that a fluid may be made toflow in the opposite direction by reversing the direction of the camshaft rotation. However, for the purpose of convenience, the descriptionof the peristaltic pump 10 will be discussed in relation to fluidflowing in the direction of arrow 16.

Before use, the tube 12 is not installed on the peristaltic pump 10 asshown in FIG. 2. The platen 28 is also in a closed position. In FIG. 2,a cover 30 for protecting a means for rotating the cam shaft 20 is shownas being detached from a frame 32 of the pump 10. However, during use,the cover 30 is attached to the frame 32 by way of screws 34. The cover30 is being shown as detached from the frame 32 for the purposes ofexplanation.

To install the tube 12 into the peristaltic pump 10, a handle 36 oflatch 38 is moved upward in the direction of arrow 40. This releases thelatch 38 and allows the platen 28 to be rotated upward in the directionof arrow 42 as shown in FIG. 4. With the platen 28 uncovering theplurality of pistons 14 a-h, the tube 12 can be mounted to the pump 10as shown in FIGS. 5 and 6. In particular, the tube 12 may have apositioning pin 44. The positioning pin 44 may have a post 46. Thepositioning pin 44 may additionally have a clip 48 that captures thetube 12. The clip 48 may be secured to the tube 12 so that the tube 12cannot slide within the clip 48. For example, the clip 48 may be adheredto the tube 12 with adhesive, epoxy, etc. As the fluid is moved throughthe tube 12 by way of sequential pressure from the pistons 14 a-h, thetube 12 does not move but remains stationary within the peristaltic pump10 due to the positioning pin 44. On the other side of the tube 12, apinch valve 50 is mounted to the tube 12. When the pinch valve 50 ismounted to the tube 12 as shown in FIG. 5, the pinch valve 50 occludesthe tube 12 so that fluid does not flow through the tube 12 (see FIG.7A). A wedge 52 pushes against the tube 12 to block flow through thetube 12. As will be discussed later, when the platen 28 is traversed tothe closed position and the handle 36 of the latch 38 is traversed tothe locked position (see FIG. 7B), a nub 120 of the handle 36 pushesagainst a trigger 54 of the pinch valve 50 which traverses the wedge 52away from the tube 12 and allows fluid to flow through the tube 12.

With the positioning pin 44 and the pinch valve 50 mounted to the tube12, the positioning pin 44 is initially inserted into a positioning pinrecess 56 and the pinch valve 50 into a pinch valve recess 58 as shownin FIG. 6. In this position, the tube 12 cannot slide longitudinally orbe displaced because the positioning pin 44 holds the tube 12 securelyin position. Moreover, fluid does not flow through the tube 12 due tothe pinch valve 50 when the platen 28 or the handle 36 is not closed.The tube 12 between the positioning pin 44 and the pinch valve 50 islaid in a straight configuration over the plurality of pistons 14 a-h,as shown in FIG. 6. When the platen 28 is closed, the platen 28, tube 12and the pistons 14 a-h are generally parallel to each other, as shown inFIG. 10. During operation of the pump 10, the pistons 14 a-h push thetube 12 against a flat surface 60 (see FIGS. 6 and 10) of the platen 28to occlude the tube 12. The pistons 14 a-h are sequentially raised andlowered in sequential fashion to squeeze the fluid through the tube 12in the direction of arrow 16. The straight configuration of the tube 12between the positioning pin 44 and the pinch valve 50 allow for easyinsertion of the tube 12 into the pump 10. The tube 12 is easilyinsertable into the pump 10 while the pump 10 is in the horizontalposition shown in FIG. 6 as well as the vertical position shown in FIG.1.

Referring now to FIGS. 6 and 7, the platen 28 is now traversed to theclosed position (see FIG. 7) by traversing the platen 28 in thedirection of arrow 62 (see FIG. 6). The handle 36 of the latch 38 istraversed to the closed position as shown in FIG. 8 by traversing thehandle 36 in the direction of arrow 64 (see FIG. 7). The peristalticpump 10 may now be hung as shown in FIG. 1 after installation of thetube 12 into the pump 10. Also, it is contemplated that the tube 12 maybe installed into the peristaltic pump 10 as shown and described inrelation to FIGS. 2-8 while the pump 10 is in the vertical orientationas shown in FIG. 1. The tube 12 is easily installed into the pump 10because the tube 12 is in the straight configuration in the pump 10.

Referring now more particularly, to FIGS. 7A and 7B, operation of theplaten 28, latch 38 and the pinch valve 50 will be discussed. When theplaten 28 is traversed downward in the direction of arrow 62 (see FIG.6) to the closed position (see FIG. 7A), the pinch valve 50 is receivedinto a hole 122 (see FIGS. 6 and 7A). The wedge 52 of the pinch valve 50is normally in the extended position as shown in FIG. 7A by way ofbiasing spring 124. The tube 12 is squeezed by the wedge 52 so as toocclude the tube 12 and prevent the flow of fluid therethrough whilesetting up the pump 10 and tube 12. Before the platen 28 or the handle36 of the latch 38 are closed, no fluid is allowed to flow through thetube 12. When the handle 36 of the latch 38 is traversed in thedirection of arrow 64, nub 120 of the handle 36 contacts trigger 54 ofthe pinch valve 50 so that the biasing force of the spring 124 isovercome. The wedge 52 of the pinch valve 50 is urged away from the tube12 and fluid is now allowed to flow through the tube 12 as shown in FIG.7B.

The latch 38 is an over center latch. In particular, catch 126 receivespin 102 mounted to the frame 32 of the pump 10. The catch 126 has a pawl128 which has an inner surface 130. A distance 132 between a pivot axis134 of the handle 36 and a distal end of the inner surface 130 of thepawl 128 is shorter than a distance 136 between the pivot axis 134 andthe proximal end of the inner surface 130 of the pawl 128. (see FIG.7B). Distance 138 between the pivot axis 134 and the outer surface ofthe pin 102 is greater than distance 132. As such, when the handle 36 isinitially traversed to the closed position by traversing the handle 36in the direction of arrow 64, the pawl 128 initially hits or contactsthe pin 102. Since there is a physical interference, the user must pushdown on the handle 36 to overcome such resistance. As the pin 102 isreceived into the catch 126, the pin 102 is urged further into the catch126 since the distance of the inner surface to the pivot axis 134 isincreasing. The pin 102 eventually goes over the center of the pawl 128so that a force is required to lift the handle 36 and open the latch 38.When the pin 102 is received into the catch 126, the handle 36 cannot bemoved upward or to the open position without applying an upward force tothe handle 36. Moreover, the over center latch 38 provides a downwardbiasing force to the nub 120 so as to overcome the biasing force of thespring 124 of the pinch valve 50 when the handle is closed. Accordingly,when the handle 36 of the latch 38 is traversed to the closed position,the platen 28 is secured in the closed position and the pinch valve 50can now allow fluid to flow through the tube 12.

Referring now to FIG. 9, the pistons 14 a-h are traversed to theextended position by way of lifters 26 a-h. The lifters 26 a-h pivotabout pivot axis 66. The lobes 24 a-d of the cams 18 a-h pushes rollers86 at distal ends of the lifters 26 a-h upward. As the rollers 86 at thedistal ends of the lifters 26 a-h moves upward, humps 68 of the lifterspushes against the pistons 14 a-h to urge the piston 14 toward theextended position. This occurs sequentially as the cam shaft 20 rotatesthe cams 18 a-h. The lifters 26 provide mechanical advantage so that asmaller motor can be used to pump more fluid through the pump. By way ofexample and not limitation, this arrangement can produce a flow rate of1500 mL through the pump.

Referring now to FIG. 11, the piston 14 defines first and second opposedends 70, 72. The hump 68 pushes against the second end 72. As the piston14 is traversed to the extended position, the first end 70 pushesagainst the tube 12 and eventually occludes the tube 12 so that fluidcannot flow through the tube 12. When the lobe 24 passes the roller 86at the distal end of the lifter 26, the tube 12, due to its resilience,pushes the piston 14 back toward the retracted position and allows fluidto flow through the tube 12 at the position of the retracted piston 14.

Referring back to FIG. 9, the cams 18 a-h are mounted to the cam shaft20. Each subsequent cam 18 is angularly displaced compared to theprevious cam 18. For example, the cam 18 b is displaced angularly withrespect to cam 18 a. Cam 18 c is displaced slightly more than 18 b. Thiscontinuous increased angular displacement of the cam 18 is continued onthrough the rest of the cams 18 d-h. As shown, the plurality of cams 18a-h are angularly displaced a bit further from each prior cam. Thisallows for the sequential movement of the pistons 14 a-h.

The cam lobes 24 a-d of the cams 18 a-h each have curved peak surfaces74 a. Referring now to FIG. 9A, the cam lobes 24 a of cams 18 a, b eachhave curved peak surfaces 74 a The curvature of the peak surface 74 a isdefined by an arc where its center is the central rotating axis 76 ofthe cam shaft 20 and the cams 18 a-h. The curved peak surfaces 24 a ofthe lobes 24 a of adjacent cams 18 a, b are synced or overlap oneanother. In particular, the curved peak surface 74 a of cam lobe 24 a ofcam 18 a maintains lifter 26 a in the up position so that the piston 14a is at the extended position. Right before the lifter 26 a is lowered,the cam lobe 24 a of cam 18 b raises the lifter 26 b to the up positionso that the piston 14 b is also at the extended position. This positionis shown in FIG. 9A. Both lifters 26 a, b are fully up and the pistons14 a, b are at the extended position. During operation, the piston 14 ais initially traversed to the extended position and occludes the tube 12(see piston 14 a of FIG. 10). The roller 86 at the distal end of thelifter 26 a rides on the curved peak surface 74 a of the cam lobe 24 aof the cam 18 a and maintains the piston 14 a in the extended positionfor a portion of the cam's rotation. The motor must be strong enough toraise the piston 14, bend and occlude the tube 12. Since the piston israised with the lifter, the lifter 26 allows for a smaller motor toaccomplish this step. During this time, cam lobe 24 a of cam 18 b raisesthe lifter 26 b up. The piston 14 b applies continuous increasingpressure to the tube 12 (see piston 14 b of FIG. 10). Since pressure isincreased and the piston 14 a occludes the tube 12 at the position ofpiston 14 a, the fluid is forced toward the direction of arrow 16. Whenthe cam lobe 24 a of cam 18 b traverses the piston 14 b to the fullyextended position, the tube 12 is occluded at the position of piston 14b. The lifter 26 a then begins its decent downward on the back side ofthe cam lobe 24 a so that additional fluid is received into the tube 12prior to the position of piston 14 b. This primes the tube 12 for thenext cycle. Piston 14 c is traversed to the extended position andapplies pressure to the tube 12 while the piston 14 b continues toocclude tube 12. The increasing pressure applied to the tube 12 bypiston 14 c urges the fluid in the direction of arrow 16. Once thepiston 14 c is in its fully extended position, piston 14 b begins toretract to the retracted position and the tube 12 at the position ofpiston 14 b accepts additional fluid. This process is repeated until thefluid is pushed through the tube 12 and out of the pump 10. This processis repeated for cam lobes 24 b, c, d of cams 18 a-h. The cam lobes 24a-d overlaps cam lobes 24 a-d of adjacent cams 18 a-h. Preferably, thecam lobes 24 a-d of the cams 18 a-h are angularly displaced an equalamount about the rotational angle of 90°. In the example shown herein,the cams 18 have four lobes 24 a-d angularly displaced 90° apart fromeach other. Accordingly, the pistons 14 a-h are cycled 4 times for eachrevolution of the cam shaft 22. Additionally, the cam lobe 24 a of thelast cam 18 h is timed to cam lobe 24 b of the first cam 18 a so thatthe peak curved surface 74 a of cam 18 h overlap with the peak curvedsurface 74 b of cam 18 a. This eliminates back flow of fluid through thepump during transition from the first set of cam lobes 24 a of the cams18 a-h to the second set of cam lobes 24 b of the cams 18 a-h.

The flow rate of fluid through the pump is based on a number ofdifferent factors. For example, the flow rate is dependent on the numberof lobes on each of the cams 18 a-h. The flow rate is also dependentupon the rotational speed of the cams 18 a-h. The flow rate may also bedependent upon the inner diameter of the tube 12. Larger inner diameterswould tend to flow more fluid through the pump than tubes with smallerinner diameters. The reason is that more fluid is displaced with largertubes as the pistons occlude the tube. However, the motor will have towork harder to drive the cams, lifters and pistons to occlude largertubes due to the increased sized of the tube itself and its resiliency.Fortunately, the lifters 26 provide mechanical advantage so that a smallmotor can still drive the cams, lifters and pistons to flow fluidthrough larger tubes. In particular, the pump 12 discussed herein may besized to flow fluid at a rate of 1500 mL or at least twice as fast asthe pump described in the '921 patent.

Referring now back to FIG. 8, the cam shaft 20 may be rotated by way ofworm gear 78, worm drive 80 and motor 82. The motor 82 may be poweredand controlled by controller 84 which is in electrical communicationwith the motor 82 by way of cable 86. The motor 82 turns the worm drive80 which turns the worm gear 78. The worm gear 78 is fixed to the camshaft 20 so that the cam shaft 20 turns as the worm gear 78 turns. Whenthe motor 82 stops turning, the cam shaft 20 does not reverse directionbecause the worm gear 78 and the worm drive 80 prevent such reverserotation. Accordingly, the fluid in the tube 12 does not flow backwardor in reverse when stopping the pump 10. The motor 82, worm drive 80 andthe worm gear 78 comprise the means for rotating the cam shaft 20discussed above which is protected by the cover 30.

Referring back to FIG. 11, the lifter 26 functions as a lever. Thelifter 26 pivots about pivot axis 66. The lobes 24 a-d of the cams 18lift up the roller 86 at the distal end of the lifter 26. The hump 68lifts up the piston 14. The hump 68 is placed about one half thedistance between the pivot axis 66 and the roller 86 of the lifter.Accordingly, if a force of X is required to lift the piston 14 andocclude the tube 12 directly under the piston 14, then a force of aboutX/2 is required to lift the roller 86 at the distal end of the lifter26. The lever principle reduces the force required to lift the piston 14by providing a mechanical advantage. This has a significant impact insizing the motor 82. In particular, the lifter 26 allows a smaller motorto turn the cams 18 a-h faster and generate a larger force through thepiston to the tube 12 so that a larger tube 12 can be installed into thepump. Moreover, the worm drive 80 and the worm gear 78 provideadditional mechanical advantage so that a smaller motor 82 can be usedto drive the pump 10.

The piston 14 is traversesable between a retracted position shown bysolid line and an extended position shown by dash lines. In the extendedposition, the first end 70 is pushed toward the flat surface 60 of theplaten 28. In this position, the distance between the first end 70 andthe flat surface 60 is less than two times the thickness of a wall ofthe tube 12. The piston 14 occludes the tube 12 when the piston 14 istraversed to the extended position. When the lifter 26 is lowered, thepiston 14 is now free to float within the through hole 100 whichreceives the piston 14. The resiliency of the tube 12 pushes the piston14 away and allows the lumen of the tube 12 to open up and allow fluidto flow through the tube 12 once again. This process is repeated duringoperation of the pump 10.

Referring now to FIG. 12, an exploded perspective view of the pump 10 isshown. The handle 36 of the latch 38 is pivotally pinned to the platen28 with pin 88. The lifters 26 are pivotally pinned to bracket 90 withpin 92. The bracket 90 is attached to the frame 32 with screws 94. Theplaten 28 is rotationally attached to the frame by way of pin 96. Therollers 86 are pinned to the distal ends of the lifters 26 by way of pin98. The pistons 14 a-h are disposed within through holes 100 formed inthe frame 32. The piston 14 is held within the through holes 100 becausea flange 106 of the bracket 90 is received into a groove 108 (see FIG.13) of the piston 14, as shown in FIG. 11. The handle 36 is removablylatched to pin 102 which is seated within the frame 32.

The process of fabricating the plurality of cams 18 a-h may beaccomplished with any known technique or any technique developed in thefuture. By way of example, as shown in FIG. 14, a plurality ofindividual cams 18 may be fabricated. Each of the cams 18 may have aplurality of through holes 104 as shown in FIG. 14A. The cams 18 may bestacked against each other and at least one through hole of adjacentcams 18 may be aligned to each other and pinned to each other. As shownin FIG. 14A, the through holes 104 are not symmetrically spread apartabout the rotating axis 76 but are angularly offset from each other. InFIG. 14A, the upper and lower holes 104 are 180 degrees apart from eachother angularly from the central rotating axis 76. Also, the left andright holes are 180 degrees apart from each other angularly from thecentral rotating axis. However, the left and right holes 104 are not 90degrees apart from the upper and lower holes 104 angularly from thecentral rotating axis 76. Rather, the left and right holes 104 areskewed from the upper and lower holes 104 angularly with respect to thecentral rotating axis 76. In this manner, different through holes 104 ofadjacent cams 18 a-h can be aligned and pinned to each other so that thecam lobes 24 of adjacent cams 18 can have a progressive angulardisplacement through the stack of cams 18 a-h. The cams 18 a-h arestackable upon each other and may be self indexing.

After the stack of cams 18 are formed, the cams 18 are disposed withinthe frame 32 as shown in FIG. 12. Radial bearings 110 are mounted to theframe 32 on opposed sides thereof. The cam shaft 20 is inserted throughthe bearings 110 and through central holes 112 of the cams 18. The lastcam 18 may have a hole 114 which is pinned to hole 116 of the cam shaft20 to mount the shaft 20 to the cams 18.

Referring now to FIG. 13A, a side profile of the piston 14 shown in FIG.13 is shown. The first end 70 may have an angled surface with a flatpeak surface 118. The flat peak surface 118 extends across a diameter ofthe piston 14 as shown in FIG. 13. The flat peak surface also ispositioned traverse to the direction of fluid flow 16 and a length ofthe tube 12 as shown in FIGS. 5 and 6. The flat peak surface 70 is heldin position because the flange 106 prevents rotation of the pistons 14a-h. When the piston 14 occludes the tube 12, the flat peak surface 118pushes against the tube 12 to occlude the tube 12.

As discussed herein, the stack of cams are described as having 8 cams 18a-h. However, it is also contemplated that the pump 10 may have more orless than eight cams. Additionally, each of the cams 18 a-h wasdescribed as having four cam lobes 24 a-d. However, it is alsocontemplated that each of the cams 18 a-h may have one or more cam lobes24. The cams 18 a-h may be formed as individual eight individual camsand stackable upon each other. The holes 104 of the cams 18 a-h are notsymmetrical and allow angular displacement of the cams 18 a-h byaligning the holes 104 of adjacent cams 18 a-h and pinning the holes toeach other. As such, the holes 104 of the cams 18 a-h allow the cams tobe self indexing. Although the cams 18 a-h may be formed individuallyand stacked upon each other, it is also contemplated that the stack ofcams 18 a-h may be formed as a unitary unit either through blow molding,machining, etc. and any method known in the art or developed in thefuture.

Moreover, as discussed herein, the pistons 14 a-h were described asbeing generally parallel to the tube and the flat surface 60 of theplaten 28. The pistons 14 a-h are constantly being traversed up and downas different timing. However, each of the pistons 14 a-h reciprocatesbetween extended and retracted positions which traverse about a commonaxis. This common axis is parallel to the tube 12 and the flat surface60 of the platen 28. The cams 18 a-h are also parallel to the pistons 14a-h, tube 12 and the flat surface 60 of the platen 28. In particular,the cams 18 a-h all have identical caming surfaces. However, thesesurfaces are angularly offset from each other. Nonetheless, the cams 18a-h share a common rotating axis 76. It is this common rotating axis 76that is parallel to the pistons 14 a-h, tube 12 and the flat surface 60of the platen 28.

The above description is given by way of example, and not limitation.Given the above disclosure, one skilled in the art could devisevariations that are within the scope and spirit of the inventiondisclosed herein, including various ways of opening the pinch valve 50upon closure of the latch 38. Further, the various features of theembodiments disclosed herein can be used alone, or in varyingcombinations with each other and are not intended to be limited to thespecific combination described herein. Thus, the scope of the claims isnot to be limited by the illustrated embodiments.

1. A peristaltic pump for flowing fluid through a lumen of a tube, thetube defining a diameter, the pump comprising: a plurality of pistonslinearly arranged adjacent to each other in a straight configuration,each of the plurality of pistons defining opposed first and second ends,each of the plurality of pistons traversable between extended andretracted positions; a plurality of lifters, each lifter being pivotableabout a pivot axis; a platen disposed adjacent to the first ends of theplurality of pistons, the platen generally parallel to the plurality ofpistons wherein a gap between the first end of one of the plurality ofpistons and the platen is about equal to or more than a diameter of thetube when the piston is traversed to the retracted position and the gapis smaller than the diameter of the tube when the piston is traversed tothe extended position; a rotatable cam shaft generally parallel to theplurality of pistons; a plurality of cams mounted to the rotatable camshaft, each of the cams having a cam lobe, the cam lobes of theplurality of cams disposable adjacent to second end portions of thelifters with the second ends of the pistons positioned in between thesecond end portions of the lifters and the pivot axis of the lifters sothat as the cam shaft rotates, the lobes raise the lifters which providea mechanical advantage to traverse the pistons to the extended position,the plurality of cams are angularly displaced with respect to theadjacent cam, the plurality of pistons being sequentially traversed tothe extended position to flow fluid through the tube.
 2. The pump ofclaim 1 wherein the platen is traverseable between an open position forinserting or removing the tube between the plurality of pistons and theplaten and a closed position for flowing fluid through the lumen of thetube when the tube is disposed between the platen and the plurality ofpistons.
 3. The pump of claim 1 further comprising: a worm gear attachedto the cam shaft; a worm drive engaged to the worm gear; a motorattached to the worm drive for rotating the worm drive.
 4. The pump ofclaim 1 wherein the plurality of pistons linearly occludes the tube aseach one of the plurality of pistons is sequentially traversed to theextended position due to the progressive angular displacement of thecams.
 5. The pump of claim 1 wherein each of the cams has four lobesspaced 90 degrees apart from each other, and a total angulardisplacement of the plurality of cam is about 90 degrees.
 6. The pump ofclaim 1 wherein the cam lobes of the cams have a curved peak surfacedefined by an arc having a center about a rotating axis of the cam shaftand the cams, the curved peak surface of cam lobes of adjacent camsoffset and overlapping one another to urge fluid through the tube in onedirection.
 7. The pump of claim 1 wherein the pistons reciprocatebetween extended and retracted positions about a common axis, and thecommon axis of the reciprocating pistons, a flat surface of the platenand a rotating axis of the cam shaft are parallel with each other.
 8. Aperistaltic pump for flowing fluid through a lumen of a tube, the tubedefining a diameter, the pump comprising: a plurality of pistonslinearly arranged adjacent to each other in a straight configuration,each of the plurality of pistons defining opposed first and second ends,each of the plurality of pistons traversable between extended andretracted positions; a platen disposed adjacent to the first ends of theplurality of pistons, the platen generally parallel to the plurality ofpistons wherein a gap between the first end of one of the plurality ofpistons and the platen is about equal to or more than a diameter of thetube when the piston is traversed to the retracted position and the gapis smaller than the diameter of the tube when the piston is traversed tothe extended position; a rotatable cam shaft disposed adjacent to thesecond ends of the plurality of pistons, the rotatable cam shaftgenerally parallel to the plurality of pistons; a plurality of camsmounted to the rotatable cam shaft, each of the cams having a cam lobe,the cam lobes of the plurality of cams disposable adjacent to the secondends of the plurality of pistons so that as the cam shaft rotates totraverse the piston to the extended position, the plurality of cams areangularly displaced with respect to the adjacent cam and the pluralityof pistons are traversed to the extended position sequentially to flowfluid through the tube.
 9. The pump of claim 8 wherein the platendefines a flat surface and the tube is squeezed between the plurality ofpistons and the flat surface in a wave format to flow fluid through thetube, the flat surface being generally parallel to the plurality ofpistons.
 10. A method of operating a peristaltic pump for flowing fluidthrough a lumen of a tube, the method comprising the steps of: disposingthe tube between a platen and a plurality of pistons wherein the tube isstraight and parallel to the platen and the plurality of pistons;sequentially traversing the plurality of pistons to an extendedposition; occluding the tube linearly down the tube when the pistons aresequentially traversed to the extended position; pushing the piston backto a retracted position due to resiliency of the tube.
 11. The method ofclaim 10 wherein the disposing step further includes the step oftraversing the platen from an open position to a closed position. 12.The method of claim 10 further comprising the step of aligning the tubeto be parallel to the platen and a cam shaft.
 13. The method of claim 10further comprising the step of rotating a cam shaft on which a pluralityof cam are mounted, each of the cams having a cam lobe angularly offsetfrom cam lobes of adjacent cams.
 14. The method of claim 10 furthercomprising the step of actuating a plurality of lifters to sequentiallytraverse the plurality of pistons to the extended position.